From: Tim Chen tim.c.chen@linux.intel.com
commit 01daf56875ee0cd50ed496a09b20eb369b45dfa5 upstream.
The logic to detect whether there's a change in the previous and next task's flag relevant to update speculation control MSRs is spread out across multiple functions.
Consolidate all checks needed for updating speculation control MSRs into the new __speculation_ctrl_update() helper function.
This makes it easy to pick the right speculation control MSR and the bits in MSR_IA32_SPEC_CTRL that need updating based on TIF flags changes.
Originally-by: Thomas Lendacky Thomas.Lendacky@amd.com Signed-off-by: Tim Chen tim.c.chen@linux.intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Jiri Kosina jkosina@suse.cz Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: David Woodhouse dwmw@amazon.co.uk Cc: Andi Kleen ak@linux.intel.com Cc: Dave Hansen dave.hansen@intel.com Cc: Casey Schaufler casey.schaufler@intel.com Cc: Asit Mallick asit.k.mallick@intel.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Jon Masters jcm@redhat.com Cc: Waiman Long longman9394@gmail.com Cc: Greg KH gregkh@linuxfoundation.org Cc: Dave Stewart david.c.stewart@intel.com Cc: Kees Cook keescook@chromium.org Link: https://lkml.kernel.org/r/20181125185004.151077005@linutronix.de Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/process.c | 42 +++++++++++++++++++++++++++--------------- 1 file changed, 27 insertions(+), 15 deletions(-)
--- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -317,27 +317,40 @@ static __always_inline void amd_set_ssb_ wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, ssbd_tif_to_spec_ctrl(tifn)); }
-static __always_inline void spec_ctrl_update_msr(unsigned long tifn) +/* + * Update the MSRs managing speculation control, during context switch. + * + * tifp: Previous task's thread flags + * tifn: Next task's thread flags + */ +static __always_inline void __speculation_ctrl_update(unsigned long tifp, + unsigned long tifn) { - u64 msr = x86_spec_ctrl_base | ssbd_tif_to_spec_ctrl(tifn); + u64 msr = x86_spec_ctrl_base; + bool updmsr = false;
- wrmsrl(MSR_IA32_SPEC_CTRL, msr); -} + /* If TIF_SSBD is different, select the proper mitigation method */ + if ((tifp ^ tifn) & _TIF_SSBD) { + if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) { + amd_set_ssb_virt_state(tifn); + } else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) { + amd_set_core_ssb_state(tifn); + } else if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) || + static_cpu_has(X86_FEATURE_AMD_SSBD)) { + msr |= ssbd_tif_to_spec_ctrl(tifn); + updmsr = true; + } + }
-static __always_inline void __speculation_ctrl_update(unsigned long tifn) -{ - if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) - amd_set_ssb_virt_state(tifn); - else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) - amd_set_core_ssb_state(tifn); - else - spec_ctrl_update_msr(tifn); + if (updmsr) + wrmsrl(MSR_IA32_SPEC_CTRL, msr); }
void speculation_ctrl_update(unsigned long tif) { + /* Forced update. Make sure all relevant TIF flags are different */ preempt_disable(); - __speculation_ctrl_update(tif); + __speculation_ctrl_update(~tif, tif); preempt_enable(); }
@@ -370,8 +383,7 @@ void __switch_to_xtra(struct task_struct if ((tifp ^ tifn) & _TIF_NOTSC) cr4_toggle_bits(X86_CR4_TSD);
- if ((tifp ^ tifn) & _TIF_SSBD) - __speculation_ctrl_update(tifn); + __speculation_ctrl_update(tifp, tifn); }
/*